Brake



Dec. 20,1933. 'EIGCARROLL 2,140,733

' BRAKE i Original Filed April 13, 1952 MMA zla A TTORNEY.

i, l Evene G. Cannon FIG Z BY Patented Dec. 20, 1938 i UNITED` STATES PATENT OFI-'ICE Bendix. Aviation Corporation,

South Bend,

Ind., a corporation of Delaware Original application April 13, 1932, Serial No.

605,083, March 23, 1937.

now Patent No.

2,074,719, dated Divided and this application May 25, 1935, Serial No. 23,426

2 Claims.

This invention relates to brakes and more specially to hydraulic operating systems there- One of the objects of the invention is to provide improved means for preventing the ingress of air into the operating parts of the system and especially into the wheel cylinders thereof.

Further objects of the invention will be apparent after a reading of the subjoined specification and claims and after a consideration of the attached drawing in which:

Figure 1 is a view showing, more or less diagrammatically, parts of a hydraulic braking system including a master cylinder, a wheel cylinder, and connections between the master cylinder and the wheel cylinder; and

Figure 2 is a view showing a modied form of wheel cylinder.

Referring in particular to the drawing, there is shown in Figure 1 a master cylinder generally designated II, a wheel cylinder generally designated I2 and iiuid connections indicated by the line I3. The cylinder II is formed of a casting I4 having a forwardly extending cylindrical portion I5 and a rearwardly extending cylindrical portion I6 having a larger diameter. On the under side of the casting'i4 there is formed a downwardly extending bracket I1 by which the cylinder II may be secured to an automotive vehicle. The upper side of the casting is formed with an annular range I8 forming a well and is exteriorly threaded as at I9 for the reception of a cover which is designed to coact with the frame to serve as a uid reservoir.

The casting II is formed at its forward end with threads 2l for the reception of an .outlet cap 22. It has a restricted inlet port 23 formed through the cylindrical portion I5 and opening into the well formed by the annular ange I8 l and has a relatively large port 24 extending diagonally through the junctionbetween the concentric cylindrical portions I5 and I6. The rear end of the casting I4 is provided with an annular iiange 25 by means of which a boot may be secured to the casting.

Secured on the threads I9 is a cylindrical cover 26 which serves together with the well formed by the flange I8 to provide a container or r`e`servoir for a reserve supply of liquid for the hydraulic braking system. 'The upper end of the cap 26 is formed with a cylindrical depression 21 having an opening 28 in the center thereof.

its lower end upon a cup valve 33. The spring 32 is of such a weight that pressure within the reservoir may be increased to a certain predetermined amount before any uid can escape past the valve which thus constitutes a spring loaded valve.

The cap 22 is provided with a tapped opening 20 into which there is threaded a pipe forming a portion of the connection I3. Secured to the rear end of the casing I4 by means of the flange 25 is a rubber boot 34 which serves to exclude dust and dirt but allows the ingress of air through an openingA 35. Passing through the boot 34 and secured thereto by a spring clip 36 is a piston rod 3l which is connected in any convenient manner to a pedal for operating the braking system. The forward end of the boot is secured over the flange 25 by a spring clip 38 and the forward end of the piston rod 31 is formed with a ball head 39 through which it is secured to a plunger or piston 40.

The plunger 40 is formed with a head 4I which substantially fills the bore of the cylindrical portion I5 and as an aid in sealing the bore, carries an annular sealing cup 42. The cup 42 may be made of rubber orother suitable material and serves to prevent the passage of uid rearward past the head 4I. The cup 42 is secured in'an annular groove 43 by means of a circular flat spring ring 44. The plunger 40 is provided with a rearwardly extending cylinder 45 which telescopes wlthin a sleeve 46 formed with a rearward ange 41 for limiting the rearward movenient of the piston 3 9 and with a fixed head 48 substantially filling the bore of the portion I6 and serving as a support for an annular sealing cup 49.

The sleeve 46 and the head 48 are prevented spring stop 5I seated in a groove 52 and are prevented from being displaced forwardly by means of a tubular member 53 which bears at its forward-end against the shoulder formed by the junction between the portions I5 and I6 and bears at its rearward end on the annular cup 49 thus serving not only to position the cylinder 46 but also serving to maintain the cup 49 in the desired position. The movable head 4I and the xedhead 48 are each formed with a plurality of small ports such as 54 and 55v respectively through which luid-may pass forwardly.

The wheel cylinder I2 comprises a cylindrical casting 6I formed with an upstanding annular flange or boss 62 which forms a well within which there is positioned a ball 6.3 normally adapted to from being displaced rearwardly by means of a ,ball 63 upon its seat.

4ing cups 13, 14, 15 and .16 respectively, said cups serving to prevent the exit or ingress of fluid from or into the wheel cylinder. It is to be noted that the cups 14 and 16 face outward while the cups 13 and 15 face inward. The plunger 66 is provided with a port 11 leading from the interior of the wheel cylinder to the groove 68 and with a port 18 leading to the atmosphere from the groove 69. The plunger 61 is similarly provided with ports 19 and 8|. The plungers are also provided with inwardly extending projections 83 and 84 which position the plungers to insure that the inlet opening 82 from the conduit I3 shall always remain open.

In preparing the hydraulic brake system shown in Figure 1 for operation, the plug 29 and the valve 33 are removed and the reservoir 26 is filled with suitable'liquid. The plug 65 is backed off from its seat so as to allow the check valve 63 to move at times oi of its seat in the bleeding' operation. Reciprocation of the rod 31 and the piston formed by the movable head by means of the pedal, forces any air trapped in the system out past the check valve 63 onthe forward stroke and at the same time draws liquid from the reservoir 26 through the port 24 and into the chamber formed between the fixed head 48 and the movable head 4|. On the rearward stroke liquid from between two heads is sucked past the movable head by reason of the vacuum created in the system ahead of said movable head. On the next forward stroke, this liquid together with thev trapped air is forced out past the check valve 63. Reciprocation is continued until the system is completely lled with liquid and until all air is driven out from the system.

Thereupon the plug 65 is screwed down to' maintain the check valve 63 upon its seat and the valve 33 and the plug 29 are reinserted in the position shown in the drawing. Thereafter, reciprocation of the plunger 40 serves to apply the brakes through the wheel cylinder. When the reservoir is first lled and bled and the assembly including theplug 29 inserted, the pressure on the liquid in the reservoir is approximately atmospheric. The movement of the plunger 40 forward forces liquid to the wheel cylinders and thus lowers the pressure in the reservoir. On account of this lowering of pressure and because no air can enter through the valve 33, some air is drawn in through the vent 35 and the ports 55 and is subsequently compressed in the upper end of the reservoir 26 to maintain the liquid in the system under super- 65 charged pressure, the amount of such pressure being controlled by the weight of thel spring 32.

The wheel cylinder 9| shown in Figure 2 is substantially the same as the cylinder I2 previously described and is provided with an annular boss or projection ||4 corresponding to the projection 62. However, a oating tubular member ||5 is provided for holding the cups ||6 and ||1 in position when the uid in the cylinder is not under brake applying pressure. It is to be understood that when operating pressure is applied to the iiuid, the fluid itself maintains the cups in their position. The plungers are also provided with additional packing cups ||6 and ||1a smaller in area and facing outward. It is possible to make the cups I6a and |1a smaller than the cups ||6 and ||1 for the reason that cups ||6 and ||1 have to accommodate the floating tubular member l5. The projection |4 is internally threaded as at ||8 and has screwed therein a plug ||9 formed with a conical end adapted to seat in a conical shaped valve seat concentric with' the projection I4.4 The plug I9 is itself formed with a tapped opening |20 and with intersecting bores |2| and |22. A bleeding hose |23 provided with a check valve |24 is adapted to be threaded into the tapped opening |20 for the bleeding operation, the plug I8 being adapted to be loosened for the same operation.

In the bleeding operation of the wheel cylinder shown in Figure 2, the plug ||8 is backed off slightly from its seat and the bleedinghose |23 is attached. Then liquid is forced to the wheel cylinders and is thence forced out past the check valve |24 carrying with it any air which may be trapped in the system. 0n the return stroke, the check valve |24 prevents air from returning into the wheel cylinder. It is to be understood that during the bleeding operation, the plug ||8 is backed olf slightly from its seat.

This application is a division of my copending application Serial No. 605,083, led April ,13, 1932 issued on March 23, 1937 as Patent No. 2,074,719. v

It is to be understood that the above described embodiments of my invention are for the purpose of illustration only and various changes may be made therein without departing from the spirit and scope of the invention.

I claim:

1. In a hydraulic brake system a Wheel cylinder, a pair of plungers in said wheel cylinder, a. pair of annular packing cups associated with each plunger, the outer cups facing outwardly and the inner'cups facing inwardly and being of larger cross-section than the outer cups, and a sleeve between the pistons accommodated by the larger cross-section of the inner packings to hold them in position.

2. In a hydraulic brake system a cylinder, a pair of plungers in said cylinder, a pair of annular packing cups, one associated with each of said pistons and facing each other, and a relatively small tubular member interposed between said cups and normally holding said cups in position.

EUGENE G. CARROLL. 

